Integrated overcurrent and overvoltage apparatus for use in the protection of telecommunication circuits
An integrated overvoltage and overcurrent circuit protection device for use in telecommunication circuits. The integrated circuit protection device combines a overcurrent device such as a fuse and a overvoltage protection device such as a thyristor to respectively protect against overcurrent conditions and transient overvoltages. Integration of the two devices in a common package ensures proper coordination and matching of the components, reduces the final product cost and reduces the physical space required on a telecommunications circuit for overvoltage and overcurrent circuit protection.
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This application is a Continuation-In-Part of U.S. application Ser. No. 09/534,277, filed Mar. 24, 2000.
BACKGROUND OF THE INVENTIONThe present invention relates to overvoltage and overcurrent protection apparatus for telecommunication circuitry and method of manufacturing same. In particular, the invention relates to fuses and thyristors.
Circuitry, particularly sensitive circuitry such as that found in telecommunication systems, require protection against both overcurrent and overvoltage conditions that may arise. Conditions such as short circuits may arise requiring an overcurrent protection device, such as a fuse, in order to prevent damage to circuitry.
Lightning is a common source of overvoltage in communication systems. Typically, communication systems consist of conductors in shielded cables suspended on poles or buried in the earth. The cable is made up of many conductors arranged in twisted pairs, commonly known as “Tip” and “Ring” lines for telephone systems, in particular. These cables are susceptible to transient energy from lightning and may conduct energy from the lightning to either a central office or subscriber equipment. Additionally, power sources for telecommunication systems are usually obtained from commercial power lines, which are also subject to excess energy from lightning that can, in turn, induce overvoltages in the telecommunication system being supplied by the power line.
Common approaches in the art to mitigate overcurrents and overvoltages include a combination of a fuse and a semiconductor overvoltage device such as a bi-directional thyristor, as shown in the circuit of
In order to limit overvoltage conditions, an overvoltage device such as the bi-directional thyristor 110 is connected across the twisted pair 102 in parallel with the telecommunication system 108. The thyristor 110 provides bi-directional “crow-bar” clamping of transients that may occur for either polarity. In particular, the thyristor 110 has a breakdown voltage at which a transient voltage exceeding this value will cause the thyristor 110 to begin clamping action across the lines 104 and 106. As the transient voltage attempts to rise higher, the current through the thyristor 110 will increase until a break-over voltage is reached. At this point, thyristor action is triggered and the thyristor 110 switches to its “on” or “latched” state. This is a very low impedance state that shunts or “crow-bars” the line, thereby suppressing the magnitude of the transient voltage. When the transient voltage diminishes, the thyristor 110 turns off and reverts to a high impedance “off” state.
The circuit of
The protection circuits used in telecommunication applications, such as that shown in
There is a need for an improved circuit device that achieves both overcurrent and overvoltage protection in a discrete integral package to more easily assure coordination and matching of the overcurrent and overvoltage devices. In addition, there is a need for a discrete integral package approach that affords lower final product cost and reduces the physical space consumed in a printed circuit.
These and other advantages are provided by the present invention, where overcurrent and overvoltage protection devices are packaged in a common housing to form a single discrete circuit element that is substantially no larger than one of the overcurrent or overvoltage devices that are each discretely packaged as previously known in the art, such as a standard surface mount telecommunications fuse, for example.
In an embodiment, the present invention provides an integral circuit protection device providing overcurrent and overvoltage protection for a circuit that is configured to be connected to the circuit. The device includes an overcurrent protection portion, an overvoltage protection portion, and a plurality of terminals for connecting both the overvoltage and overcurrent protection portions of the integral circuit device to the circuit to be protected. Incorporation of both overvoltage and overcurrent devices into a single housing assures that these components are coordinated and matched for a particular application, lowers the total cost of the device since the components are not sourced separately and allows for smaller size by incorporating the devices into the same package.
In another embodiment the plurality of terminals includes first, second and third terminals with the overcurrent protection portion electrically connected between the first and second terminals and the overvoltage protection portion connected between the second and third terminals.
In another embodiment, the overcurrent protection portion includes a fuse.
In another embodiment, the overvoltage protection portion includes a bi-directional thyristor.
In another embodiment, the plurality of terminals of the integral circuit are configured to electrically connect the overcurrent protection portion in series with the circuit to be protected and to electrically connect the overvoltage protection portion in parallel with the circuit to be protected when the integral circuit device is electrically connected to the circuit to be protected.
In yet another embodiment, the integral circuit further includes a thermally conductive portion that conducts heat away from the overvoltage protection portion.
In an embodiment, thermal coefficients of the thermally conductive portion and overvoltage protection portion are substantially the same.
In an embodiment, the overvoltage protection portion is at least partially encapsulated with an atmospherically resistant material.
In another embodiment, the integral circuit device is configured for mounting on a printed circuit board.
In another embodiment, the integral circuit device is configured substantially the same as a standard telecommunications fuse configuration.
In yet another embodiment of the present invention, a circuit element is provided for overvoltage and overcurrent protection of a circuit. The circuit element includes a circuit element housing having first, second and third terminals. An overcurrent protection device is electrically connected between the first and second terminals and contained by the circuit element housing. In addition, an overvoltage protection device is electrically connected between the second and third terminals and also contained by the circuit element housing.
In an embodiment, the circuit element housing is comprised of a tube having an outer surface, an inner hollow portion, a first end and a second end. The overcurrent protection device is disposed within the inner hollow portion of the tube, the overvoltage protection device and the second terminal are disposed on the outer surface of the tube, the first terminal is disposed at the first end and the second terminal is disposed at the second end opposite from the first terminal.
In another embodiment, the first and second terminals include electrically conductive layers disposed on the outer surface of the tube adjacent to each of the first and second ends and extending into part of the inner hollow portion adjacent to the first and second ends. Additionally, conductive end caps respectively cover the electrically conductive layers and the first and second ends and electrically connected to the electrically conductive layers. The electrically conductive layers are also electrically connected to the overcurrent device disposed within the inner hollow portion of the tube.
In yet another embodiment, the third terminal is comprised of a conductive terminal disposed on the outer surface of the tube.
In another embodiment, a die bond pad disposed on the outer surface of the tube. A bond pad conductor is also disposed on the outer surface of the tube and electrically connected to at least one of the first and second conductive layers. A first conductor electrically connects the bond pad conductor to the die bond pad die bond pad and a second conductor electrically connects the third terminal to the die bond pad. A thyristor is disposed on the die bond pad and covered with an encapsulant material.
In an embodiment, the encapsulant material is atmospherically resistant and disposed such that the thyristor and the die bond pad on the outer surface of the tube are sealed to resist surrounding atmosphere.
In another embodiment, the thyristor disposed on the die bond pad is bonded to the die bond pad by a thermally conductive bonding material.
In an embodiment, the circuit element housing includes a substrate having first and second surfaces and a plurality of wire terminations disposed on at least one of the first and second surfaces, wherein the first, second and third terminals are each respectively comprised of one of the plurality of wire terminations.
In an embodiment, the overcurrent device is comprised of a fuse element electrically connected between the first and second terminals and disposed on at least one side of the substrate. The overvoltage device is comprised of a thyristor electrically connected between the second and third terminal and disposed on at least one side of the substrate.
In a further embodiment of the present invention, a circuit element is provided for overvoltage and overcurrent protection for circuitry in a telecommunications system. The circuit element includes a fuse element, a semiconductor overvoltage protection device, and a package configured as a discrete component that is mountable on a printed circuit board, the package containing the fuse element and the semiconductor overvoltage protection device.
In another embodiment, the package includes first, second and third terminals. In addition, the fuse element and the semiconductor overvoltage protection device both include corresponding first and second lead connections. The first terminal is connected to the first lead connection of the fuse element, the second terminal is connected the second lead connection of the fuse element and the first lead connection of the semiconductor overvoltage protection device and the third terminal is connected to the second lead connection of the semiconductor overvoltage protection device.
In a still further embodiment of the present invention, the invention provides a method for providing an overcurrent and overvoltage device in a telecommunications circuit. The method includes providing a housing configured to receive an overcurrent protection element and an overvoltage protection element, the housing having a plurality of terminals. The overcurrent and overvoltage protection elements are disposed within the housing such that the overcurrent protection element is electrically connected between first and second terminals of the plurality of terminals and the overvoltage protection element is electrically connected between the second terminal and a third terminal of the plurality of terminals. Finally, the housing is connected as a single discrete element to a circuit board that includes the telecommunications circuit.
In an embodiment, the method includes electrically connecting one of the first and second terminals to a first incoming line to the telecommunications circuit and electrically connecting the other of the first and second terminals to the telecommunications circuit such that the overcurrent protection element is connected in series with the telecommunications circuit, and electrically connecting the third terminal to a second incoming line to the telecommunications circuit such that the overvoltage protection element is connected in parallel with the telecommunications circuit.
In a further embodiment, the present invention provides an integral circuit protection device providing overcurrent and overvoltage protection for a circuit and configured to be connected to the circuit, wherein the device includes an overcurrent protection portion; an overvoltage protection portion, and a plurality of terminals for connecting both the overvoltage and overcurrent protection portions of the integral circuit protection device to the circuit to be protected, such that a part of the overvoltage protection portion also serves as one of the plurality of terminals.
In another embodiment, the integral circuit protection device further includes a second overcurrent protection portion, a second overvoltage protection portion, and fourth and fifth terminals as part of the plurality of terminals, wherein the second overcurrent protection portion is electrically connected between the fourth and fifth terminals, the second overvoltage protection portion is connected to the fifth terminal, a part of the second overvoltage protection portion jointly serves as the third terminal, and the third terminal is connected to ground.
In a further embodiment, an integrally formed bond pad and connector piece is connected between the second terminal and the overvoltage protection device.
In yet another embodiment of the present invention, a method is provided for an overcurrent and overvoltage device in a telecommunications circuit which includes the steps of: providing a mounting member configured to receive an overcurrent protection element and an overvoltage protection element, the mounting member having a plurality of terminals; disposing the overcurrent and overvoltage protection elements within the mounting member such that the overcurrent protection element is electrically connected between first and second terminals of the plurality of terminals, the overvoltage protection element is electrically connected to the second terminal, and a part of the overvoltage protection element serves as a third terminal of the plurality of terminals; and connecting the mounting member as a single discrete element to a circuit board that includes the telecommunications circuit.
In another embodiment, the method further includes providing the mounting member with both a second overcurrent protection element and a second overvoltage protection element, and disposing the second overcurrent and overvoltage protection elements within the mounting member such that the second overcurrent protection element is electrically connected between fourth and fifth terminals of the plurality of terminals and the second overvoltage protection element is electrically connected between the third and fifth terminals of the plurality of terminals.
Additional advantages and features of the present invention will become apparent upon reading the following detailed description of the presently preferred embodiments and appended claims, and upon reference to the attached drawings.
Reference is made to the attached drawings, wherein elements having the same reference numeral represent like elements throughout and wherein:
The present invention provides a single discrete component that includes an overcurrent protection element and an overvoltage protection element enclosed by a common housing. Additionally the present invention provides methods of manufacturing same.
Referring now to the drawings,
As shown in
Preferably, the thyristor 302 is constructed with a vertical structure that it is substantially flat having a cathode on one surface and an anode on the opposing surface. Accordingly, when the thyristor 302 is placed on the die bond pad 206, one of the cathode or anode is in electrical contact with the die bond pad 206 and the other opposing thyristor terminal (i.e., either the anode or cathode) faces away from the tube 200. Hence, connection with the opposing terminal to the bond pad 208 requires either a bond wire or a bond strap 304.
Finally,
Additionally,
Additionally, a bi-directional thyristor 504 is disposed on a surface (i.e., surface 507 of
In a preferred embodiment, the fuse element 502 and bi-directional thyristor 504 are disposed on the same surface of the substrate 500, as are terminals 506, 508 and 510. Additionally, the fuse element 502 and bi-directional thyristor 504 are encapsulated within a encapsulant 512 to protect these elements from atmospheric conditions and also to contain energy dissipated by these elements during either overcurrent or overvoltage conditions. Furthermore, the substrate 500 is constructed of a thermally conductive material in order to draw heat away from components 502 and 504.
Preferably, for both disclosed embodiments, the thermal coefficients (PCE) of the substrate 500 and the thyristor are substantially the same.
Referring now to
Turning to
The bi-directional thyristor 619 shown in
With respect to the embodiments shown in
As shown in the circuit of
The circuit of
The bottom side of the overcurrent and overvoltage protection device of
Turning now to
The common packaging of the overcurrent protective fuse element and the overvoltage protective thyristor element of the present invention provides the assurance that these components are properly coordinated and matched. For example, given a telecommunication circuit requiring protection of overvoltages of 600 volts or greater and short circuit conditions of 40 amps or greater, the thyristor and fuse elements can be selected accordingly and incorporated into a common package. Thus, for specific telecommunications circuits, the common circuit element of the present invention is constructed such that the thyristor and fuse elements meet regulatory and safety requirements for particular circuits without the need to ensure that both components are properly coordinated and matched as required in the prior art discrete component approach.
Additionally, by incorporating the fuse element and thyristor in a common package, the additional space requirements for two discrete component packages is eliminated, thereby reducing the physical space needed in a telecommunication circuit for overvoltage and overcurrent circuit protection. Moreover, an integrated overvoltage and overcurrent circuit element avoids problems associated with separately sourcing components and interconnecting those components made by different suppliers. This approach further reduces the cost of the final product since a single manufacturer supplies a singular overvoltage and overcurrent circuit protection element.
Reducing costs and complexity even further is the embodiment of the present invention which uses one or more thyristor elements of the overcurrent and overvoltage protection device as Terminal C. Indeed, to the extent that the fabrication of the device is substantially directed to only one side, manufacturing costs again likely would be reduced. Such a configuration also offers lower circuit impedance given the more direct path between components.
It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its attended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.
Claims
1. An integral circuit protection device providing overcurrent and overvoltage protection for a circuit and configured to be connected to the circuit, comprising:
- an overcurrent protection portion;
- an overvoltage protection portion having an at least partially conductive surface; and
- a plurality of terminals for connecting both the overvoltage and overcurrent protection portions of the integral circuit protection device to the circuit to be protected, wherein the at least partially conductive surface of the overvoltage protection portion serves as one of the plurality of terminals, wherein the circuit protection device is formed as a discrete component for mounting on a printed circuit board, and wherein the plurality of terminals contact a surface of the printed circuit board upon placement thereon.
2. The integral circuit protection device of claim 1, wherein the plurality of terminals includes first, second and third terminals, the part of the overvoltage protection portion serving as one of the plurality of terminals being the third terminal, the overcurrent protection portion being electrically connected between the first and second terminals, and the overvoltage protection portion being connected to the second terminal.
3. The integral circuit protection device of claim 1, wherein the overcurrent protection portion includes a fuse.
4. The integral circuit protection device of claim 1, wherein the overvoltage protection portion includes a bi-directional thyristor.
5. The integral circuit protection device of claim 1, wherein the plurality of terminals are configured to electrically connect the overcurrent protection portion in series with the circuit to be protected and to electrically connect the overvoltage protection portion in parallel with the circuit to be protected when the integral circuit protection device is electrically connected to the circuit to be protected.
6. The integral circuit protection device of claim 1, further comprising:
- a thermally conductive portion that conducts heat away from the overvoltage protection portion.
7. The integral circuit protection device of claim 6, wherein thermal coefficients of the thermally conductive portion and overvoltage protection portion are substantially the same.
8. The integral circuit protection device of claim 2, wherein the first, second and third terminals are formed on at least one same side of the integral circuit protection device.
9. The integral circuit protection device of claim 1, wherein the integral circuit protection device is configured for mounting on a printed circuit board.
10. The integral circuit protection device of claim 1, wherein the integral circuit protection device is configured substantially the same as a standard telecommunications fuse configuration.
11. The integral circuit protection device of claim 2, further comprising:
- a second overcurrent protection portion;
- a second overvoltage protection portion;
- fourth and fifth terminals as part of the plurality of terminals; and
- wherein the second overcurrent protection portion is electrically connected between the fourth and fifth terminals, the second overvoltage protection portion is connected to the fifth terminal, a part of the second overvoltage protection portion jointly serves as the third terminal, and the third terminal is connected to ground.
12. The integral circuit protection device of claim 11, further comprising:
- a third overvoltage protection portion connected between the third terminal and ground.
13. A circuit element for overvoltage and overcurrent protection of a circuit, comprising:
- a circuit element mounting member having first, second and third terminals, wherein the circuit element is formed as a discrete component for mounting on a printed circuit board, and wherein the first, second and third terminals contact a surface of the printed circuit board upon placement thereon;
- an overcurrent protection device electrically connected between the first and second terminals, the overcurrent protection device being contained by the circuit element mounting member; and
- an overvoltage protection device electrically connected to the second terminal and being contained by the circuit element mounting member, wherein a part of the overvoltage protection portion is conductive and serves as the third terminal.
14. The circuit element of claim 13, wherein the circuit element mounting member is further comprised of a tube having an outer surface and an inner hollow portion;
- wherein the overcurrent protection device is disposed within the inner hollow portion of the tube, and each of the overvoltage protection device, the first terminal and the second terminal is disposed on the outer surface of the tube.
15. The circuit element of claim 13, wherein the overcurrent protection device is a fuse configured to protect the circuit from excessive currents.
16. The circuit element of claim 13, wherein the overvoltage protection device is a thyristor configured to protect the circuit from excessive voltages.
17. The circuit element of claim 14, wherein the tube further has a first end and a second end, the first terminal being disposed at the first end, and the second terminal being disposed at the second end opposite from the first terminal.
18. The circuit element of claim 17, wherein the first and second terminals include electrically conductive layers disposed on the outer surface of the tube adjacent to each of the first and second ends and extending into part of the inner hollow portion adjacent to the first and second ends;
- wherein conductive end caps respectively cover the electrically conductive layers and the first and second ends and are electrically connected to the electrically conductive layers; and
- wherein the electrically conductive layers are electrically connected to the overcurrent device disposed within the inner hollow portion of the tube.
19. The circuit element of claim 13, further comprising:
- an integrally formed bond pad and connector piece connected between the second terminal and the overvoltage protection device.
20. The circuit element of claim 13, wherein the overcurrent device is electrically connected in series with the circuit to be protected and the overvoltage protection device is electrically connected in parallel with the circuit to be protected.
21. The circuit element of claim 13, wherein the circuit element mounting member further comprises:
- a substrate having first and second surfaces; and
- a plurality of wire terminations disposed on at least one of the first and second surfaces, wherein at least the first and second terminals are each respectively comprised of one of the plurality of wire terminations.
22. The circuit element of claim 21, wherein the overcurrent protection device is comprised of a fuse element electrically connected between the first and second terminals and disposed on at least one side of the substrate, and the overvoltage protection device is comprised of a thyristor electrically connected to the second terminal and disposed on at least one side of the substrate.
23. The circuit element of claim 21, further comprising:
- an atmospherically resistant encapsulant disposed on at least one side of the substrate and having a fuse element and thyristor therebetween.
24. The circuit element of claim 21, wherein the first, second and third terminals are formed on at least a same side of the circuit element.
25. The circuit element of claim 21, further comprising:
- an integrally formed bond pad and connector piece connected between the second terminal and the overvoltage protection device.
26. The circuit element of claim 13, wherein the circuit element mounting member is comprised of a thermally conductive material.
27. The circuit element of claim 14, further comprising:
- a second overcurrent protection device;
- a second overvoltage protection device;
- fourth and fifth terminals; and
- wherein the second overcurrent protection device is electrically connected between the fourth and fifth terminals, the second overvoltage protection device is connected to the fifth terminal, a part of the second overvoltage protection device jointly serves as the third terminal, and the third terminal is connected to ground.
28. The integral circuit device of claim 27, further comprising:
- a third overvoltage protection device connected between the third terminal and ground.
29. A method for providing an overcurrent and overvoltage device in a telecommunications circuit, the method comprising the steps of:
- providing a mounting member configured to receive an overcurrent protection element and an overvoltage protection element, the mounting member having a plurality of terminals;
- disposing the overcurrent and overvoltage protection elements within the mounting member such that the overcurrent protection element is electrically connected between first and second terminals of the plurality of terminals, the overvoltage protection element is electrically connected to the second terminal, and a part of the overvoltage protection element is conductive and serves as a third terminal of the plurality of terminals;
- connecting the mounting member as a single discrete element to a circuit board that includes the telecommunications circuit;
- electrically connecting one of the first and second terminals to a first incoming line to the telecommunications circuit and electrically connecting the other of the first and second terminals to the telecommunications circuit such that the overcurrent protection element is connected in series with the telecommunications circuit; and
- electrically connecting the third terminal to a second incoming line to the telecommunications circuit such that the overvoltage protection element is connected in parallel with the telecommunications circuit.
30. The method of claim 29, further comprising the steps of:
- providing the mounting member with both a second overcurrent protection element and a second overvoltage protection element; and
- disposing the second overcurrent and overvoltage protection elements within the mounting member such that the second overcurrent protection element is electrically connected between fourth and fifth terminals of the plurality of terminals and the second overvoltage protection element is electrically connected between the third and fifth terminals of the plurality of terminals.
31. The method of claim 30, further comprising the step of:
- providing the mounting member with a third overvoltage protection element; and
- disposing the third overvoltage protection element within the mounting member such that the third overvoltage protection element is electrically connected between the third terminal and ground.
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- Harris Surgectors for Telecommunications System—pp. 10-149/10-156.
Type: Grant
Filed: Aug 28, 2000
Date of Patent: Jan 3, 2006
Assignee: Littelfuse, Inc. (Des Plaines, IL)
Inventor: Stephen J. Whitney (Lake Zurich, IL)
Primary Examiner: Gary L Laxton
Attorney: Bell, Boyd & Lloyd LLC
Application Number: 09/649,195
International Classification: H02H 3/22 (20060101);